This Asthma and Allergic Diseases Center Grant application is an effort to continue a long-standing fruitful collaboration among 4 UCSF faculty members with a long-standing interest in the mechanisms underlying allergic airway inflammation and asthma. The central goals of this application are to determine critical mechanisms underlying the initiation and persistence of allergic airway inflammation and airway hyperresponsiveness. The application includes two projects that will utilize murine models and a third that will examine the relevance of molecular targets and pathways identified in these models to asthma prevalence, severity and drug responsiveness in humans. The Center Principal Investigator and leader of Project 1, Dean Sheppard, has identified critical roles for activation of transforming growth factor ? (TGF??) by two different integrins (?v?6 and ?v?8) in airway hyperresponsiveness in a chronic model of allergic asthma and in modulation of cognate immune responses. This proposal will take advantage of a series of lines of genetically modified mice to directly examine the role of TGF?? in these effects, to determine the critical cells types responsible, and to identify the molecular mechanisms underlying these responses. Project 2 is based on recent data from Richard Locksley, the project leader, that chitin, a prominent structural component of fungi, parasites and crustaceans, activates macrophages and primes innate immune cells for initiation of type 2 immune responses. Work proposed in this project will utilize a series of novel reporter lines to examine the critical chitin-responsive cells and the mechanisms and relevance of this pathway for initiation of allergic inflammation. Project 3, co-led by Esteban Burchard and John Fahy will follow-up on preliminary observations about genetic associations between sequence variants in chitin-degrading enzymes and TGF?? and allergic sensitization and asthma to more deeply interrogate associations and gene-gene interactions for sequence variants in chitinases and multiple components of the TGF? activation and signaling pathways, including the integrin subunits examined in Project 1. This project will also evaluate the functional significance of associated genes using bronchoalveolar lavage samples and tissue from asthmatic patients and healthy control subjects. These projects will be supported by a Physiology and Tissue Analysis core that will provide extensive support for all 3 projects, and by a centralized Administrative core. Lay summary - This Center will evaluate the mechanisms underlying initiation and persistence of asthma. By identifying novel pathways and molecular targets and testing their relevance to asthma, asthma severity and drug response in humans, the work in the Center should provide clues for the development of new treatments for this common and often devastating disease. PROJECT 1: ?v Integrins in Cognate Immunity and Airway Hyperresponsiveness (SHEPPARD, D) PROJECT 1 DESCRIPTION (provided by applicant): Mice lacking the epithelial integrin, ?v?6, that we have shown activates latent TGF-?, are protected from the persistent airway hyperresponsiveness (AHR) that follows chronic allergen challenge. Surprisingly, this protection is not associated with any decrease in sub-epithelial airway fibrosis, a central TGF-? -dependent feature of this model. Mice with leukocyte specific knockout of the related integrin, ?v?8, which also activates TGF-? show evidence of enhanced adaptive immunity. In this proposal, we will determine whether these altered responses in ?v?6 subunit knockout mice are a direct consequence of loss of the ?v?6 integrin and/or of TGF-? activation from conducting airway epithelial cells using rescue mice expressing either the wild type integrin or active TGF-? in airway epithelial cells. We will evaluate the effects of ?v?6 antibodies and a TGF-? RII-lg chimera on these same endpoints to further confirm the importance of this pathway and evaluate the feasibility of targeting this pathway for therapeutic intervention. To determine the mechanisms by which loss of ?v?6 protects from induction of AHR, we will evaluate the relationship between airway responsiveness and expression of a small number of candidate genes identified as linked to this phenotype in preliminary experiments utilizing expression microarrays. We will also determine the cellular distribution of expression by immunostaining and/or in situ hybridization, and will evaluate functional significance using commercially available lines of mice expressing null mutations of specific candidates. Because the cytokine IL-13 is known to play a central role in induction of AHR in multiple models, and because two of the most promising candidates identified by microarrays, leukotrienes C4 synthase and interleukin-18 have been suggested to be upstream of IL-13 induction in the airways, we will also examine the cellular sources of IL-13 in chronically challenged wild type and ?v?6 knockout mice. Finally, we will determine how loss of leukocyte ?v?8 leads to enhancement of adaptive immunity and examine the relevance of this pathway to allergic airway inflammation and its consequences. Lay summary - This project will examine how a single growth factor, transforming growth factor ?, can either contribute to development of chronic asthma or inhibit allergic sensitization and its consequences, depending on where and how this growth factor is activated.